Olefin conversion process

ABSTRACT

AN OLEFIN OR MIXTURES OF OLEFINS ARE CONVERTED TO MORE COMPLEX CHEMICAL COMPOUNDS SUCH AS DIMERS BY CONTACT WITH A LIQUID METAL AT AN ELEVATED TEMPERATURE. BENZENE AND 1,5-HEXADIENE ARE FORMED ON PASSING A MIXTURE OF PROPYLENE AND AIR THROUGH A MOLTEN MASS COMPOSED OF BISMUTH AND TIN.

United States Patent Oflice 3"786109 Patented Jan. 15, 1974 3,786,109OLEFIN CONVERSION PROCESS Arthur L. Jones, Solon, Ohio, assignor to TheStandard Oil Company, Cleveland, Ohio No Drawing. Continuation-impart ofabandoned application Ser. No. 760,991, Sept. 19, 1968. This applicationApr. 12, 1971, Ser. No. 136,181

Int. Cl. C07c 3/20 US. Cl. 260--673 2 Claims ABSTRACT OF THE DISCLOSUREAn olefin or mixtures of olefins are converted to more complex chemicalcompounds such as dimers by contact with a liquid metal at an elevatedtemperature.

Benzene and 1,5-hexadiene are formed on passing a mixture of propyleneand air through a molten mass composed of bismuth and tin.

complex compounds.

Dehydrodimerization of monoolefins has previously been carried out at atemperature above 300 C. in the presence of a catalyst such as an oxideof lead, cadmium, or thallium as described in French Pat. No. 1,473,718.In this prior art process the feed is composed of the moolefin andoxygen. The presence of oxygen causes the production of carbon dioxideas a by-product. Accordin to this prior art process propylene isconverted to 1,5-hexadiene, isobutylene is converted to2,5-dimethyl-1',5-hexadiene, and alpha-methyl styrene is converted to2,5-diphenyl-1,5-hexadiene. According to this prior art disclosure thecatalytic dehydrodimerization reaction can also be used to converttoluene to dibenzyl, acetonitrile to succinonitrile and acetic acid tosuccinic acid.

According to British Pat. No. 1,084,743 relatively high molecular weightdienes are produced by thermal treatment of certain specifiedmonoolefinic compounds British Patent No. 1,084,743 discloses thatcompounds of the y R-CH:-JJ=+ I Ra wherein R must be a secondary ortertiary alkyl radical, R R and R are hydrogen, alkyl, etc., can beconverted by pyrolysis at a temperature in the range of 660 F. to 1850F. in the absence of a catalyst to compounds of the type I plusby-products. Oxygen is not necessaryin this prior art process, althoughinert materials such as paraflinic hydrocarbons, benzene, nitrogen,helium and carbon monoxide can be included in the feed. Inert solids mayalso be used such as magnesia, glass, Pyrex, quartz, Carborundum and thelike. a

I have discovered a process for converting an olefin or a mixture ofolefins to more complex chemical compounds comprising contacting theolefin, optionally with oxygen or an oxygen-containing gas such as air,with a liquid metal or mixture of liquid metals at an elevatedtemperature, below, above or substantially at atmospheric pressure.

The olefins useful in the anstant process are preferably olefinichydrocarbons having (from 12 to 20 carbon atoms. The olefinichydrocarbons may be monoolefinic or polyolefinic hydrocarbons such asethylene, propylene, the butylenes, the amylenes, the hexenes,cyclohexene, the heptenes, the octenes, the nonenes, the decenes, theundecenes, the dodecenes and the like; butadiene, isoprene,2,3-dimethylbutadiene, piperylene, Z-neopentyl butadiene- 1,3 and thelike and others. Most preferred olefinic hydrocarbons are themonoolefinic hydrocarbons having from 2 to 6 carbon atoms.

The liquid or liquified metal useful in this invention can be any metalor alloy which exists as a liquid under the preferred reactionconditions of the process of this invention. Preferred metals which canbe used alone or in combination are bismuth and tin.

The preferred reaction conditions for the process of this invention are(from about 200 C. or lower to 1200 C. or higher and pressures at ornear atmospheric, below atmospheric or above atmospheric. Most preferredconditions are from about 350 C. to about 650 C. and about atmosphericpressure. Contact times on the order of 0.2

of metals can be used as isothermal reaction media by passing reactantsthrough a mass of the liquid medium and allowing the resultant bubblesto climb by gravity through the medium. It is also preferred that thefeed by efficiently dispersed in the liquid metal for more etficientcontact. It is believed that the instant process is carried out undernearly perfect isothermal conditions which is a decided advantage.According to an article by C. F. Cullis, Industrial and EngineeringChemistry, vol. 59, December, 1967, page 21:

Since most oxidation processes are highly exothermic, another importantphysical consideration is the ease of removal of the heat of reaction,since, if there is a runaway increase of temperature, only completecombustion of the hydrocarbon will take place. To facilitate themaintenance of as nearly as possible isothermal conditions, long narrowcatalyst beds are frequently used and the catalyst may also be dilutedwith an inert solid, per haps using the greatest dilution at the inletend where the partial pressure of the reactants are highest. 7 Thetemperature of the liquid metal used as reaction medium in the instantprocess can be maintained to a close tolerance because of its excellentheat transfer properties. Thus, it is believed that the instant processis nearly an ideal isothermal process and has none of the run-awaypotential associated with prior art processes. Although the exactmechanism of the chemical reactions which occur in this process are notknown with any degree of certainty, it is believed that hydrogen isextracted from the olefins to form radicals and that these radicalscombine to form the more complex compound products. -When the process iscarried out in the substantial absence of molecular oxygen, the majorprod ucts areoligomers such as dimers and trimers of the olefin andhydrogen. When appreciable amounts of molecular oxygen are present inthe feed, the main products are oligomers and water. When oxygen is usedin the feed there are also oxygenated products and carbon oxidesproduced in minor quantities.

Propylene, for instance, can readily be converted to 1,5-hexadiene bythe process of this invention and isobutylene is converted to2,5-dimethyl-1,5-hexadiene. These diene products may be used for manypurposes. Thus, from such dienes there can be manufactured many resinsand polymers which are valuable for the preparation of fibers andfilaments. The dienes can undergo the x0 reaction to form diols usefulas solvents or as intermediates in the manufacture ofother resins. The1,5-dienes can be selectively isomerizedto conjugated dienes which havemany usefuYapplications, e.g., reaction with maleic anhydride.Typically, 2,5-dimethyl-1,5-hexadiene can be converted to2,5-dimethyl-2,4-hexadiene. The latter material can be polymerized tohigh-melting point and high molecular-weight polymers using anappropriate catalyst, e.g., boron trifiuoride catalyst.

According to this invention, reaction conditions can be selected wherebycyclic oligomers such as benzene can be produced from propylene andxylenes can be produced directly from isobutylene. In general, very fewoxygenated products are produced by this process; however, conditionscan be adjusted so that propylene oxide and ethylene oxide can beproduced from propylene and ethylene, respectively.

In the following example which will further illustrate this invention,the amounts of all ingredients are expressed as parts by weight unlessotherwise indicated.

EXAMPLE The reactor employed was a large Pyrex glass tube having aspherical ground glass cap with two entry ports. The bottom section wasequipped with a side-arm for product Withdrawal. The diameter of thereactor was about two inches and the overall height was about nineinches. The side-arm was located about six inches up from the bottom ofthe reactor. The depth of the liquid metal in the reactor was usuallymaintained at about 4 /2 inches. A Pyrex glass gas dispersion tubehaving a medium or coarse porous tip was used to introduce the reactantsinto the liquid metal at a point below the surface of the liquid metal.A small stainless steel tube was fit concentrically inside thedispersion tube. Air or oxygen was fed through the outside annulus ofthe concentric tube arrangement and hydrocarbon gases were fed throughthe center tube.

The reactants were mixed as they passed through the porous glass tip ofthe dispersion tube. The mixed gases were passed up through the moltenmetal as bubbles until they broke through the upper surface of theliquid, Where the gaseous products were withdrawn through the side-arm.

The residence time of a bubble of reactants in the liquid metal usingthe above-described apparatus is about 0.5 second. The time is almostindependent of flow rate. Because bubble size is determined by size ofthe pores in the gas disperser, changes in flow rate produce more orfewer bubbles of about the same size which require about the same timeto rise through the melt regardless of the number of them. At very highflow rates bubbles will coalesce to produce larger bubbles which willclimb more quickly. Less satisfactory results are obtained under thelatter conditions. The most practical way to change residence time(contact time) is to change the height of the liquid metal through whichthe bubbles rise.

The reactants were contained in pressure gas cylinders. Pressure wasreduced through regulator valves and the rate of gas flow to the reactorwas controlled by rotameters. The hydrocarbon regulator pressure was setat 10 p.s.i.g. and air and nitrogen pressures were set at 15 p.s.i.g.The gases may be mixed after coming from the rotameters and beforeentering the reactor. The reactor was immersed in a radiant heatelectric coil furnace, the temperature of which was regulated by avariable transformer and a temperature controller. A thermowell havingtwo thermometers for temperature indication and regulator was located inthe mass of liquid metal.

As the product gases came from the reaction zone, they were passedthrough a glass sample collector. The gas samples were analyzed by gaschromatography and sometimes also by mass spectrometry. The reaction wasmonitored by means of a vapor fractometer which had two room temperaturecolumns. One column was made up of a 10-foot long, 118-inch tube packedwith 13 molecular sieves. This column was capable of resolving hydrogen,oxygen, nitrogen, carbon monoxide and methane. The second column waspacked with Chromosorb P (4050 mesh) having 30 feet impregnated withacetonyl acetate and 10 feet with benzyl ether. The second column wascapable of resolving C C C hydrocarbons and carbon dioxide.

(A) In this manner a mixture of propylenezair in the mole ratio of 1:2,respectively, was passed through a molten mass composed of one part byweight of bismuth metal and one part by weight of tin metal which wasmaintained at 1100 F. The propylenezair mixture was fed at the rate of80 cc. per minute and the gaseous product had the following compositionon a weight basis:

Percent Propylene 87.36 (:0 4.43 CO 0.05 Ethylene-ethane 1 .0 6 Methane0.45 C; 0.25 1,5-hexadiene 1.86 Benzene 4.53

catalyst which is a member selected from the group consisting of moltenbismuth, molten tin, and mixtures thereof, in the range of from about350 C. to about 650 C.

2. The process of claim 1 wherein the contact time is from 0.2 up to 3.0seconds.

References Cited UNITED STATES PATENTS 260348.5 F, 680 R, 683.15 R

